[Numpy-discussion] argsort question

Charles R Harris charlesr.harris at gmail.com
Thu Jun 8 10:34:05 CDT 2006


Robert,

Modifying your example gives

In [3]: import numpy as nm

In [4]: a = nm.zeros( 10000 )

In [5]: b = nm.arange( 10000 )

In [6]: nm.alltrue( a.argsort(kind="merge" ) == b )
Out[6]: True


On 6/8/06, Robert Cimrman <cimrman3 at ntc.zcu.cz> wrote:
>
> Hi all,
>
> I have just lost some time to find a bug related to the fact, that
> argsort does not preserve the order of an array that is already sorted,
> see the example below. For me, it would be sufficient to mention this
> fact in the docstring, although having order preserving argsort is also
> an option :). What do the developers think?
>
> In [33]:a = nm.zeros( 10000 )
> In [34]:b = nm.arange( 10000 )
> In [35]:nm.alltrue( nm.argsort( a ) == b )
> Out[35]:False
>
> r.
>
>
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